linux-kernel - Re: [syzbot] [net?] possible deadlock in ptp_clock

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Message-ID: <tencent_F746F768976CA6D1936EE37F2964E3ACA405@qq.com>
Date: Tue, 10 Jun 2025 09:01:01 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+eb6f218811a9d721fd53@...kaller.appspotmail.com
Cc: andrew+netdev@...n.ch,
	andrew@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	pabeni@...hat.com,
	richardcochran@...il.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] possible deadlock in ptp_clock_unregister

> syz-executor421/5891 is trying to acquire lock:
> ffff888079fcc868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_vclock_in_use drivers/ptp/ptp_private.h:103 [inline]
> ffff888079fcc868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_clock_unregister+0x21/0x250 drivers/ptp/ptp_clock.c:415
> 
> but task is already holding lock:
> ffff8880300cc868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: n_vclocks_store+0xf1/0x6d0 drivers/ptp/ptp_sysfs.c:215
They are not the same lock.
> 
> other info that might help us debug this:
>  Possible unsafe locking scenario:
> 
>        CPU0
>        ----
>   lock(&ptp->n_vclocks_mux);
>   lock(&ptp->n_vclocks_mux);
> 
>  *** DEADLOCK ***